Halogenated aromatic sulfone or ketone compounds can be produced by the Lewis-acid catalyzed condensation of a halogenated aromatic compound containing sulfonyl or carbonyl groups with an aromatic hydrocarbon. For example, 4,4'-bis(p-chlorophenylsulfonyl)biphenyl can be produced by reacting p-chlorobenzenesulfonyl chloride with biphenyl using nitrobenzene as a solvent in the presence of a Lewis acid catalyst such as ferric chloride or aluminum chloride. Compared with aluminum chloride, ferric chloride is a preferred catalyst because it displays both high activity and product selectivity. The crude 4,4'-bis(p-chlorophenylsulfonyl)biphenyl product mixture contains unreacted p-chlorobenzenesulfonyl chloride, bis(p-chlorophenyl) sulfone which is an impurity in the p-chlorobenzenesulfonyl chloride, 4-(p-chlorophenylsulfonyl)biphenyl which is the monohalophenylsulfonyl-substituted product, and inorganic impurities such as, for example, iron-containing compounds when ferric chloride is used as catalyst. It has been found that in scaling-up this preparation of the aromatic sulfone or ketone compounds, the iron content in the product mixture is increased.
Halogenated aromatic sulfone or ketone compounds can be used in a variety of applications. For example, the halogenated aromatic sulfone or ketone compounds can be used as monomers in the production of high-temperature arylene sulfide sulfone and arylene sulfide ketone polymers.
When the halogenated aromatic sulfone or ketone compounds are used as monomers for arylene sulfide polymers, these side products act as chain terminators during polymerization and therefore must be removed. Furthermore, the iron contaminant interferes with the polymerization process for preparing the arylene sulfide polymers from the monomers as well as imparts color to and changes physical properties of the resulting arylene sulfide polymers. Therefore, it is necessary to purify the halogenated aromatic sulfone or ketone compounds.
Purification of the desired halogenated aromatic sulfone or ketone compounds has been a problem due to low solubility in most organic solvents and the very similar solubility of undesirable monohalo-substituted reaction products. Traditional recrystallization processes can produce high purity halogenated aromatic sulfone or ketone compounds, but they have the disadvantages of low throughput, difficulty in removing residual solvent, and difficulty in scaling to pilot plant or commercial operations. Therefore, a purification process which is economical, commercially viable, and can utilize inexpensive solvents to produce high purity product with good yield is highly desirable.